Generally, in the case of a conventional battery using a lithium (Li)-free metal oxide as a cathode active material, it is necessary to use Li metal as an anode in order to provide a Li source. However, if Li metal reacts with water, hydrogen gas is generated and a rapid exothermic reaction occurs. Moreover, Li metal shows high reactivity to an electrolyte at high temperature. Therefore, in such batteries, safety-related problems occur due to the use of Li metal.